Virtualization of networks is common in modern datacenters for various applications. Virtualization allows datacenter tenants to create a network with an addressing scheme that is suitable for various workloads and also allows the tenant administrator to set networking policies within their network as they see fit.
These virtualized tenant networks are an overlay atop of the underlying physical network of the datacenter. The networking interfaces in a tenant virtual machine (VM) are therefore connected directly to the virtualized tenant network (or the overlay network). Switches, which are aware of both Virtualized networks and the physical networks, perform appropriate transformations to ensure that packets are delivered to and from the virtualized network endpoints in a way that both the overlay endpoints and the underlay endpoints are unaware of the specifics of the network virtualization intended by the tenant administrators.
Programming of virtualization aware switches is typically done by a software defined network (SDN) controller. An SDN controller may maintain a repository of the intended networking state in the datacenter and also incorporate logic to achieve that state, e.g. by programming switches.
Load balancing is a typical function desired in modern datacenters. Load balancers map virtualized IPs (VIP) to a set of Data Center IPs (DIPs). DIP endpoints may represent endpoints inside the virtualized network of a tenant. VIPs are typically internet or at least datacenter routable, i.e., they are not typically virtualized. DIPs on the other hand are typically virtualized. In order to perform the translation between non virtualized (VIP) endpoints and virtualized (DIP) endpoints, load balancers running under an SDN controller must be aware of the network virtualization policies that the SDN controller intends to achieve in the datacenter. Load balancers must also work in concert with other components in the SDN controller to achieve load balancing of workloads virtualized in the tenant space.
In a typical datacenter, hosts sometimes need to be taken out of service for example, for servicing, maintenance, upgrades to server software, etc. In such cases, tenant workloads are typically live migrated to another host so that the workloads experience minimal or no down time. In the live migration scenario, CPU context for all processes running within the migrated workload is ensured to be restored on the destination host. In a similar way, it is also beneficial to ensure that the network flows terminating at the migrating workload are restored at the destination host. This is also true for flows originating outside the datacenter such as those coming over a load balancer.
In other cases, DIP endpoints may not be virtualized, such as if they are associated with VMs that contribute to a datacenter's infrastructure. These DIPS may also be behind or work in conjunction with a load balancer and/or be live migrated. As used herein, a DIP endpoint may be virtualized or non-virtualized.
Probes are typically employed by load balancers to ascertain health of DIP endpoints behind a load balancer VIP. The list of DIP endpoints serving a VIP may be updated based on the probe status reported from each of the possible DIP endpoints. However, the effects of live migration on probing, which may negatively affect the probing process, have not been addressed.